Rolling mill system

ABSTRACT

A rolling mill system has oppositely driven, temperature-controlled first and second rolls, each having a first roll half with a first end face, a second roll half with a second end face, and a roll center. The first roll has a peripheral surface with open grooves arranged on the first and second roll halves and with ribs between the grooves. The grooves of the roll halves are arranged opposed to one another at an obtuse angle and symmetrically to the roll center. The width of the ribs is smaller than the width of the grooves. The grooves extend continuously between the end faces. The second roll has a smooth peripheral surface. First and second cutting devices are arranged at the first and second end faces of the first roll, respectively. The cutting devices are arranged near open ends of the grooves.

[0001] The invention relates to a rolling mill system having thefeatures of the preamble of claim 1.

[0002] Such a rolling mill system is disclosed in EP 0 231 398. Thisrolling mill system is a continuous mixing and shearing rolling millsystem for shearing and simultaneously transporting by means of groovesa material that can be plasticized. By means of a strip cutting roller,material is removed in the form of strips that are subsequently cut by atransverse cutting device to granules. Disadvantageously, themanufacture of granules is relatively complex with this rolling millsystem.

[0003] Other rolling mill systems with shearing action on the materialas a result of grooves provided on peripheral surfaces of two rolls aredisclosed in EP 0 148 966, EP 0 324 800, DE 43 30 090 C2, DE 43 34 697A1, and DE-OS 23 56 201.

[0004] The object of the invention resides in that the rolling millsystem of the aforementioned kind is to be further developed so that anoptimal manufacture of granules can be achieved.

[0005] For solving this object, it is proposed according to theinvention that the rolling mill system according to the preamble ofclaim 1 is configured in accordance with the characterizing portion ofthis claim.

[0006] Because of the special arrangement of grooves, the material istransported quickly to the two end faces of the roll. During transport,the ribs act as cooling ribs. Since the width of the ribs is smallerthan the width of the grooves, practically no shearing action is causedwhen rotating the rolls but only a transport action; this makes therolling mill system particularly effective. Accordingly, in a very shortperiod of time a large amount of material can be transported outwardlyby means of the grooves and can be processed to granules by means of thecutting devices. In this way, overall an optimal manufacture of granulescan be achieved by means of the rolling mill system according to theinvention

[0007] The grooves can extend across the entire width of each roll halfbeginning at the roll center and reaching to the end face of the roll,respectively. However, it is also conceivable to have the grooves extendonly across a certain partial area of the width of each roll half. Thispartial area is the edge area of each roll half that is associated withthe respective end face. The remaining area free of grooves of each rollhalf is then smooth. The length of the grooves matches in such anembodiment approximately one quarter of the corresponding roll diameter.

[0008] The material to be processed is filled into the roll nip betweenthe two rolls. In order to always provide sufficient material forprocessing, a special embodiment of the invention provides that theperipheral surface of at least one roll is provided with a recess in thearea of the roll center. The recess extends over the entirecircumference of the roll and can be curved or rectangular when viewedin the direction of the axis of rotation of the roll. The grooves thatextend from the roll center to the end faces are advantageously arrangedrelative to the axis of rotation of the roll at an angle of up to 450.In this way, between oppositely positioned rolls of the individual rollhalves an angle of 180° to 900 is produced. The width of the ribs isbetween 0.5 times to a little less than 1 time the width of the grooves.

[0009] The invention will be explained in more detail in the followingwith the aid of the drawing. The drawing shows one embodiment of theinvention. It is shown in:

[0010]FIG. 1 a side view;

[0011]FIG. 2 a plan view according to FIG. 1;

[0012]FIG. 3 a broken-off cross-section view of the two rolls with rollnip according to FIG. 1; and

[0013]FIG. 4 a broken-off plan view onto a roll having a cutting deviceaccording to FIG. 1.

[0014] The rolling mill system according to the invention has two rolls1, 2 having axes that are parallel to one another and being rotatablysupported on a frame 3 provided with a drive motor 4 that isspeed-controlled. The roll 1 can be driven by the roll 2 by means of agear pair, wherein the roll 1 acts as a so-called working roll and theroll 2 as a so-called counter roll. On the roll surface of the roll 1,on the first (right) roll half 5 and on the second (left) roll half 6open grooves 7, 8 are arranged on each half, respectively. Theperipheral surface of the roll 2 is usually of a smooth configuration.The grooves 7 of the first roll half 5 and the grooves 8 of the secondroll half 6 of the roll 1 meet at the roll center 9 at an obtuse anglewherein the grooves 7, 8, as illustrated in FIG. 2, extends continuouslyfrom the first end face 10 of the first roll half 5 to the second endface 11 of the second roll half 6. At each end face 10, 11 of the roll 1a cutting device 12 is provided in the area of the open ends of thegrooves 7, 8. The cutting device 12 is a rotating disk knife that isspring-adjusted against the end faces 10, 11. The grooves 7, 8 areuniformly distributed about the periphery of the roll 1, have a width ofbetween 0.5 mm and 10 mm, preferably between 1 mm and 8 mm, and have adepth of between 0.5 mm and 20 mm. The groove depth of the roll 1corresponds at least to the groove width. It is maximally three timesthe groove width. The groove depth can increase up to twice the initialvalue from the product feed at the roll center 9 to the product exit atthe two end faces 10, 11 of the roll 1. In this way, in an embodiment ofa roll with a diameter of 200 mm the groove depth can be 2 mm in thearea of the roll center 9 and 4 mm at the edge of the roll. Between thegrooves 7, 8, metal ribs 13, 14 are arranged that extend parallel to thegrooves. The width of the ribs 13, 14 is smaller than the width of thegrooves 7, 8. Preferably, the width of the ribs 13, 14 is between 0.5times and less than 1 time the width of the grooves. Each groove 7, 8can be, for example, 3 mm wide and each rib 13, 14 can be 2 mm wide. Thegroove shape is formed by two lateral parallel extending sidewalls andpasses into a semi-round shape at the base. A dovetail-shaped wideningof the groove up to the base of the groove is advantageous. In order forthe material to be interlocked within the grooves, the cross-section ofthe groove shape can also be V-shaped or of another shape that isbeneficial for material transport.

[0015] The grooves 7, 8 are arranged at a slant and are positioned at anangle of 20° relative to the axis of rotation of the roll 1 or at acorresponding angle of 70° relative to the axis of the roll center 9.The conceivable angle range for the grooves 7, 8 can be from 0° up to45° relative to the axis of rotation or from 90° up to 45° relative tothe axis of the roll center 9.

[0016] The length of the grooves 7, 8, which, according to oneembodiment, are arranged in a partial area of the width of each rollhalf 5, 6 in the vicinity of both end faces 10, 11 of the roll 1, is atleast 10 mm and, depending on the diameter of the roll, is up to 150 mm.In this connection, the length of the grooves corresponds toapproximately a quarter of the respective diameter of the roll. Theremaining groove-free area of the roll 1 is smooth. In the illustratedembodiment according to FIG. 1, the grooves 7, 8 extend from the rollcenter 9 across the entire width of each roll half 5, 6 to therespective end faces 10,11.

[0017] The roll 1 has across the entire length a cylindrical surface;the roll 2 has a special surface contour or recess 19. Beginning at thetwo ends of the roll 2, a cylindrical area 15 is provided, respectively,opposite the half-open grooves 7, 8 arranged on the roll 1. Thiscylindrical area 15 of the surface contour of the roll 2 forms togetherwith the metal ribs 13, 14 of the roll 1 a roll nip 16 close to zerobetween the rolls 1 and 2 and closes the half-open grooves 7, 8 whenpassing through the roll nip. This cylindrical area 15 of the roll 2,depending on the roll diameter, has a length of 10 mm to 150 mm. In theembodiment having a roll diameter of 200 mm, the cylindrical area 15 hasa length of approximately 50 mm.

[0018] In FIG. 3, schematically a section of the roll nip 16 formedbetween the rolls 1 and 2 is illustrated in the area of the grooves 7,8. A product 17 is fed to the roll nip 16 by means of an external feedopening 18. Downstream of the cylindrical area 15 of the surface contourof the roll 2 in the direction toward the roll center 9, a conicallydecreasing diameter or recess 19 of the roll 2 is provided so that inthis area an enlargement of the roll nip 16 from near zero to apredetermined value between 1 mm and maximally approximately 20 mm,preferably between 2 mm and 5 mm, is provided at the roll center 9. Thesurface contour or recess 19 in the area of the roll center 9 can bearc-shaped, as illustrated in FIG. 2, but also rectangular orroof-shaped or can have any other suitable shape. This transition areabetween the two cylindrical areas 15 of the surface contour serves forguiding the product or plastic material 17 away from the roll center ofthe roll 2 into the grooves 7, 8. Moreover, the larger roll nip 16provided at the roll center 2 enables build-up and stabilization of amaterial overlap of the product 17 that is fed onto the roll 1 from theexterior.

[0019] In an embodiment with a roll length of 200 mm, a roll diameter of200 mm, and an angle of the grooves 7, 8 of 20° relative to the axis ofrotation, the length of the grooves 7, 8 for each roll half 5, 6 isapproximately 105 mm and the length of the cylindrical section 15 of theroll 2 for each roll half is approximately 50 mm. Across the totallength of the grooves 7, 8, the groove depth increases fromapproximately 2 mm at the roll center 9 in the direction toward both endfaces 10, 11 to approximately 4 mm.

[0020] When operating the rolling mill system according to theinvention, the grooves 7, 8 arranged in the two roll halves 5, 6 of theroll 1 are filled with plastic material as a result of the pressureproduced in the roll nip 16. Because of the oppositely turning rolls 1,2, with each pass through the roll nip the excess amount of material 17is pressed out of the openings of the grooves 7, 8 at the two end faces10, 11 in the form of short strand sections 20. These strand sections 20are then cut off by the two rotating disk knives 12 and are thrown offas granules 21. The granules 21 fall onto a riddle sifter or onto afluidized bed, are mixed with already cooled-down granules in order tobe subsequently stored in the solidified state in the correspondingstorage containers. The shape of the half-open grooves 7, 8 determinesthe outer shape of the granules 21; the length of the pressed-out strand20 provides its height. The length of the granules 21 is adjustable fora constant feed of the plasticized material by means of the rotationalspeed of the roll. In this connection, low rotational speeds providelonger strand sections, higher rotational speeds shorter strand sections20. The rotational speed range for the rolling mill system according tothe invention can be adjusted between 5 and 500 rpm.

[0021] The plasticized product 17 coming from the roll center 9 of theroll 1 must be temperature-controlled before entering the grooves 7, 8such that on the roll 1 a visco-plastic material will form which isstill deformable but firm with regard to cutting. The granules shouldnot immediately stick together after the cutting process. An intensivetemperature control of the two roll surfaces from the interior and/orfrom the exterior therefore serves for providing a fine adjustment ofthe product viscosity in the range of firmness for cutting the material.In the case of greater throughput quantities, an extended residence timeon the roll or a larger roll diameter can be required for an exacttemperature control of the product layer. Depending on the application,the length of the roll is accordingly 0.5 times up to 8 times thediameter of the roll. For longer rolls with a length of more than 1.5times the roll diameter, the material transport is improved by thearrangement of flat mirror-symmetrically and oppositely oriented grooveson the surface of the roll 2. The grooves of the roll 2 are arrangedrelative to the grooves of the roll 1 mirror-symmetrically to the nipaxis of the roll nip 16. These additional grooves on the roll 2 have thesame angle relative to the axis of rotation, the same rib width, and thesame groove width as the grooves 7, 8 on the roll 1, but they have adepth that is only approximately one third in comparison to the groovedepth of the roll 1. For exact simultaneous rotation of both rolls 1, 2,the contours of the grooves 7, 8 in the roll 1 and the contour of thegrooves in the roll 2 together provide the contour of the granules 21.

[0022] With the special oppositely oriented arrangement of the grooves7, 8 on the two roll halves 5, 6 as well as a smaller width of the ribs13, 14 relative to the width of the grooves 7, 8, an effective and fasttransport of the material 17 to be processed is enabled to the cuttingdevices 12 where the material strand 20 is cut to form granules 21. Inthis way, the rolling mill system according to the invention is suitablein an optimal way for producing granules.

What is claimed is: 1-9. (cancelled)
 10. A rolling mill systemcomprising: a first roll and a second roll that are oppositely drivenand temperature-controlled; wherein the first and second rolls eachcomprise a first roll half having a first end face, a second roll halfhaving a second end face, and a roll center; wherein the first roll hasa peripheral surface provided with open grooves arranged on the firstand second roll halves and with ribs remaining between the grooves;wherein the grooves of the first roll half and the grooves of the secondroll half are arranged opposed to one another at an obtuse angle andsymmetrically to the roll center, wherein a width of the ribs is smallerthan a width of the grooves; wherein the grooves of the roll extendcontinuously from the first end face to the second end face; wherein thesecond roll has a peripheral surface that is smooth; a first cuttingdevice arranged at the first end face of the first roll and a secondcutting device arranged at the second end face of the first roll,wherein the first and second cutting devices are arranged in an area ofopen ends of the grooves.
 11. The rolling mill system according to claim10, wherein the peripheral surface of at least one of the first andsecond rolls has a circumferential recess at the roll center.
 12. Therolling mill system according to claim 10, wherein the grooves arearranged at an angle of up to 45° relative to an axis of rotation of thefirst roll.
 13. The rolling mill system according to claim 10, whereinthe width of the ribs is between 0.5 times the width of the grooves andless than 1 times the width of the grooves.
 14. The rolling mill systemaccording to claim 10, wherein the grooves have a width of between 0.5mm and 10 mm and a depth of between 0.5 mm and 20 mm, wherein a depth ofthe grooves matches at least the width of the grooves.
 15. The rollingmill system according to claim 10, wherein the depth of the groovesincreases from the roll center up to the first and second end faces. 16.The rolling mill system according to claim 10, wherein the first andsecond cutting devices each comprise a disk knife that isspring-adjusted against the first or second end face, respectively.